Aircraft and hybrid with magnetic airfoil suspension and drive

ABSTRACT

An aircraft is disclosed that comprises a fuselage with first and second wings non-rotatably secured to and extending from sides of the fuselage. Inner and outer tracks are secured to and encircle the fuselage, and airfoils are operably secured between the inner and outer tracks. Means are provided for rotating the airfoils. The means for rotating the airfoils may be comprised of first and second drive coils, and first and second alternators may be operably coupled to the first and second drive coils, respectively, to provide redundant power supplies. Permanent magnets in the rotor hub may be arranged in a Halbach array or may be arranged to provide a series of alternating, opposite magnetic poles. Separate drive and suspension coils may be provided in the stator. The concept may find further application in a lift fan or tail section of conventional aircraft. In that regard, a lift fan or tail section may be provided in which a stator magnetically levitates a lift fan rotor or tail rotor. The stator may include suspension coils and drive coils to eliminate the need for a drive shaft and gears to power the lift fan rotor or tail rotor.

This application is a continuation-in-part of U.S. Provisional PatentApplication No. 60/204,182, filed on May 15, 2000.

BACKGROUND OF THE INVENTION

This invention relates to aircraft, and more particularly, to arotorcraft hybrid that incorporates a magnetic or electromagneticvertical takeoff and landing (“VTOL”) system or an aircraft that uses amagnetic suspension and drive for a tail rotor or lift fan.

Conventional helicopters or rotorcraft are versatile aircraft that allowfor vertical takeoff and landing and that offer reasonable amounts ofvertical lift and horizontal speed up to the retreating blade limit. Thebasic helicopter configuration is the result of mechanical evolutionthat applied the present state of the art over many years. While theconventional rotorcraft offers many advantages, it still suffers from anumber of disadvantages. For example, rotor blades are long but providemeaningful lift over only a relatively short segment at the ends of therotor blades. This means that the center of the rotor area is not beingeffectively utilized. Also, because the hub about which the rotor bladesrotate is relatively small, only a small number of airfoils may be used.Similarly, because the rotor shaft is relatively small, the weight ofthe craft and any load carried may place significant stress on theshaft. These disadvantages severely restrict the lift capabilities ofrotorcraft. Further, having the center of gravity displacedsubstantially below the center of lift leads to a relatively unstableconfiguration. Further still, the horizontal speed of conventionalrotorcraft is undesirably limited by the retreating blade limit. Also, atail rotor is needed for stability, and tail rotors of conventionalhelicopters suffer from a number of problems. For example, mechanicallinkages, such as drive shafts and gears, that mechanically couple tailrotors to main engines add unnecessarily to the weight of helicoptersand can cause mechanical and reliability problems.

Conventional fixed wing aircraft are versatile as well and offer manyadvantages. Aerodynamic advantages allow fixed wing aircraft to travelat greater speeds and carry heavier payloads. Still, conventional fixedwing aircraft typically lack VTOL capabilities. Hybrid aircraft such asthe Harrier, Osprey, and Joint Strike Fighter have been developed in anattempt to offer a fixed wing aircraft having VTOL capabilities or veryshort takeoff and landing (“VSTOL”) capabilities. While these areremarkable aircraft, they too suffer from a number of shortcomings. Forexample, the vertical lift capabilities of these aircraft is quitelimited and do not approach the vertical lift capabilities offered bymany conventional helicopters, so they are poor candidates fortransporting heavy payloads. Also, these aircraft are relativelyunstable during VTOL or VSTOL maneuvering. Further still, mechanicallinkages, such as drive shafts and gears, that mechanically couple liftfans and turbine engines can add unnecessarily to the weight of aircraftsuch as the Joint Strike Fighter and can lead to mechanical andreliability problems.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide arotorcraft or rotorcraft hybrid that combines the VTOL capabilities of arotorcraft with the speed of a fixed wing aircraft.

It is a further object of the present invention to provide a craft ofthe above type that offers superior lift capabilities.

It is a further object of the present invention to provide a craft ofthe above type that offers horizontal speed that is not limited by thespeed of the retreating blade.

It is a further object of the present invention to provide a craft ofthe above type that offers superior stability during takeoff, landing,and cruising.

It is a further object of the present invention to provide a craft ofthe above type in which a majority of the airfoil length is used toprovide lift.

It is a further object of the present invention to provide a craft ofthe above type in which the center of mass of the craft is located at ornear the center of lift.

It is a further object of the present invention to provide a craft ofthe above type that offers aerodynamic shrouding of the airfoils.

It is a further object of the present invention to provide a craft ofthe above type that offers stealthy shrouding of the airfoils.

It is a further object of the present invention to provide a craft ofthe above type that uses electromagnetic means to suspend and drive theairfoils.

It is a further object of the present invention to provide a craft ofthe above type that provides strong, light rotor and stator hubs thatallow for consistent drive and suspension despite some radial expansionof the rotor hub during operation.

It is a further object of the present invention to provide a craft ofthe above type that uses an increased number of airfoils for added liftcapabilities.

It is a further object of the present invention to provide a craft ofthe above type that uses two sets of counter-rotating airfoils forincreased stability without the need for a tail rotor.

It is a further object of the present invention to provide a craft ofthe above type that provides for safe continued suspension and drivingof the airfoils in the event of a partial power failure.

It is a still further object of the present invention to provide a craftof the above type that provides for continued suspension and rotation ofthe airfoils even in the event of a total power failure.

It is a still further object of the present invention to provide a craftof the above type that incorporates a tail rotor or lift fan of a typethat eliminates the need for a drive shaft and gears.

It is a still further object of the present invention to provide a craftof the above type that incorporates a tail rotor or lift fan in which arotor is magnetically levitated and driven by a stator.

Toward the fulfillment of these and other objects and advantages, theaircraft of the present invention comprises a fuselage with first andsecond wings non-rotatably secured to and extending from sides of thefuselage. Inner and outer tracks are secured to and encircle thefuselage, and airfoils are operably secured between the inner and outertracks. Means are provided for rotating the airfoils. The means forrotating the airfoils may be comprised of first and second drive coils,and first and second alternators may be operably coupled to the firstand second drive coils, respectively, to provide redundant powersupplies. Permanent magnets in the rotor hub may be arranged in aHalbach array or may be arranged to provide a series of alternating,opposite magnetic poles. Separate drive and suspension coils may beprovided in the stator. The concept may find further application in alift fan or tail section of conventional aircraft. In that regard, alift fan or tail section may be provided in which a stator magneticallylevitates a lift fan rotor or tail rotor. The stator may includesuspension coils and drive coils to eliminate the need for a drive shaftand gears to power the lift fan rotor or tail rotor.

BRIEF DESCRIPTION OF THE DRAWINGS

The above brief description, as well as further objects, features andadvantages of the present invention will be more fully appreciated byreference to the following detailed description of the presentlypreferred but nonetheless illustrative embodiments in accordance withthe present invention when taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is an overhead view of an aircraft of the present invention;

FIG. 2 is a rear view of an alternate embodiment of an aircraft of thepresent invention;

FIGS. 3-5 are schematic, side elevation views of alternate embodimentsof an aircraft of the present invention;

FIGS. 6-8 are sectional, side elevation views of alternate embodimentsof an aircraft of the present invention;

FIG. 9 is a schematic representation of a Halbach array of permanentmagnets;

FIG. 10 is a sectional view of taken along line 10-10 or FIG. 7, showingan internal rotor hub and stator support coils;

FIG. 11 is a sectional, side elevation view of an internal rotor hub andstator;

FIG. 12 is a sectional view taken along line 12-12 of FIG. 11;

FIGS. 13 and 14 are graphical representations of total lift of aconventional helicopter and an aircraft of the present invention,respectively;

FIG. 15 is a sectional view of an alternator for use in practicing thepresent invention;

FIG. 16 is a sectional view of a variable bypass engine including analternator;

FIGS. 17 and 18 are schematic alternate embodiments showing alternatorscoupled with drive coils of upper and lower electric motors;

FIG. 19 is a schematic view of magnetic field paths when only a singlealternator is active;

FIGS. 20-22 are diagrams of a power delivery system of the presentinvention;

FIG. 23 is a schematic view of a conventional tail rotor or lift fanrotor;

FIG. 24 is a schematic view of a tail rotor or lift fan rotor of thepresent invention;

FIG. 25 is a schematic view of downwash and turbulence encounteredduring VTOL operation of an Osprey aircraft; and

FIG. 26 is a schematic view of downwash and turbulence encounteredduring VTOL operation of an aircraft of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, the reference numeral 10 refers in general to anaircraft of the present invention. The aircraft has a fuselage 12, wings14, inner and outer tracks or stators 16 and 18 encircling the fuselage,and airfoils 20 extending between the tracks 16 and 18. Means areprovided for rotating the airfoils 20. Engines 22, such as turbineengines, may be provided.

As illustrated in FIGS. 1-4, the fuselage 12 and wings 14 may take anynumber of shapes, sizes and configurations. Also, engines 22 may beaffixed to the fuselage 12 or to the wings 14. Referring to FIG. 2, acargo area 24 may form part of or be disposed below the fuselage 12. Asshown in FIG. 3, in one alternate embodiment, the airfoils may bedisposed below the fuselage 12 similar to a hovercraft. Although notclear from the schematic representation in FIG. 3, the top surface ofthe wing is shuttered for horizontal flight. As seen in FIG. 4, weapons26, such as a large caliber gun, may be incorporated into the aircraft,and the aircraft may also include armor 28. As also seen in FIG. 4, theaircraft need not have wings 14 but may instead be used with or withouta fairing 30. As best seen in FIG. 5, when an engine 22 is affixed tothe fuselage 12, the engine may be disposed between upper and lower setsof airfoils, and an inlet air path 32 and outlet thrust path 34 may beprovided for the engine 22 to receive inlet air and to provide thrustbetween the upper and lower sets of airfoils 20. Because the airfoils 20are not disposed above the fuselage 12 as in a conventional helicopter,a safety ejection seat may be used in an aircraft of the presentinvention 10.

As illustrated in FIGS. 6-8, the rotor hubs 36, and therefore airfoils20, are magnetically levitated and driven about stators 16. A rotor hub36, stator hub 16, and associated support coils 38 and drive coils 40form a large diameter, distributed, electric motor. Each set of airfoils20, rotor hubs 36, and stators 16 are substantially identical, so onlyone of each will be described in detail. As best seen in FIG. 1, thestator hub 16 encircles the fuselage 12 to form a large diameter,circular, inner track 16. The stator hub 16 and rotor hub 36 may beshaped or configured in any number of ways for operably coupling thestator hub 16 and rotor hub 36. As seen in FIG. 6, the rotor hub 36 maybe in the shape of an external hub that mates with a protruding portionof the track or stator 16. In this embodiment, the protruding portion ofthe stator 16 is comprised of an alternating series of support coils 38and drive coils 40. The external rotor hub 36 is comprised of alightweight metal with carbon fiber bands 42 embedded therein forfurther weight reduction.

In the external rotor hub 36 embodiment depicted in FIGS. 6 and 8, threesets of permanent magnets 44 disposed in Halbach arrays are alsodisposed in the rotor hub 36 for interaction with the support 38 anddrive coils 40 in the stator 16. As best seen in FIG. 9, a Halbach arrayis an arrangement of permanent magnets 44 that results in a periodic,permanent magnetic field on one side 46 and only a small magnetic field48 on the other side, as illustrated in FIG. 9. FIG. 9 shows a Halbacharray of permanent magnets 44 and its interaction with a series ofconducting levitation and drive coils 40. Arrows 50 show theorientations of the polarities of the magnets 44, arrows 48 show how themagnetic fields cancel, and arrows 46 show how the magnetic fieldscombine. Moving the Halbach array past a series of conducting loopsinduces current in the loops, producing a magnetic field that opposesthe magnet movement and that generates a repulsive force. Electric driveof the Halbach array is accomplished by interspersing current driven,conducting loops regularly between support or suspension loops 38 thatgenerate a moving magnetic field that pulls or pushes the Halbach arrayalong the conducting loop structure. This is similar to the Inductrak™magnetically levitated train system developed at Lawrence LivermoreNational Laboratory.

As best seen in FIGS. 7 and 11, airfoil supports 52 are secured to therotor hub 36. As seen in FIG. 8, controlling the pitch of the counterrotating airfoils is also accomplished using magnetic bearings, such asHalbach bearings 54. The pitch of each airfoil 20 is controlled via apitch control arm 56 that is connected to a skate that rides in acylindrical magnetic bearing ring. The distance from the rotor hub 36 tothe bearing ring is controlled with actuators 58 so that the ringcontrols the pitch of each airfoil 20. The pitch control system issimilar to a swash plate in a conventional rotorcraft system.

In the preferred embodiment, the rotor hub 36 is an internal rotor hubsuch as shown in FIG. 7. In this embodiment, a channel 60 is formed inthe stator 16, and a flange portion of the internal rotor hub 36 fitswithin the channel 60. Sets of support coils 38 are disposed above andbelow the channel 60, and a set of drive coils 40 is disposed at aninner portion of the channel 60. Although not preferred, it isunderstood that drive coils 40 may be interspersed between support coils38 above and below the channel 60. The rotor hub 36 is comprised of alightweight metal with carbon fiber bands 42 embedded therein forfurther weight reduction. An airfoil support 52 is secured to the rotorhub 36. As seen in FIGS. 7 and 10, a series of permanent magnets 44arranged with alternating poles is disposed in a flange area of therotor hub 36. As best seen in FIG. 7, the permanent magnets 44 arecovered with a thin conductor shield 62 to prevent the drive fields fromreaching the magnets 44 and changing their magnetization. Covering thepermanent magnets 44 with a thin conducting shield 62 to preventcross-magnetization is an important feature. Although this feature maynot be clearly shown in each drawing, it is understood that otherpermanent magnets 44 found in the rotors 36 will also use a similar thinconducting shield 62. This conducting covering of the magnets 44 in theflange area also serves to center the rotor hub 36 with respect to thestator 16 because the conducting surface interacts with the magneticfields in the support coils 38. The internal rotor hub 36 configurationis shown in more detail in FIG. 11. As seen in FIG. 11, the top andbottom support coils 38 are held in place by top, center, and bottomclamps 64, secured in place with bolts 66. FIG. 12 shows the clamps 64holding the support coils 38 in place, with the internal rotor hub 36disposed between the upper and lower support coils 38. Although notdepicted, corresponding support coils 38 positioned above and below thestator 16 may be connected in series to provide a “null flux”configuration as described in more detail below.

Table 1 sets forth sample, hypothetical parameters for two,representative embodiments of the present invention, representingversions for light and heavy duty.

TABLE 1 Hypothetical Parameters of Light and Heavy Duty AircraftParameters Light Heavy Rotor Hub Parameters Rotor Hub diameter 5 m 10 mRotor Hub circumference 15.7 m 37.68 m Number of sectors 12 28 Number ofairfoils/sector 1 1 Lift and Drag per Airfoil Airfoil length 1.2 m 2 mAirfoil chord 0.5 m 0.5 m Air density 1.29 kG/m³ 1.29 kG/m³ Liftcoefficient 0.8 0.8 Drag coefficient 0.05 0.05 Avg airfoil velocity 100m/s 100 m/s Airfoil area 0.6 m² 1 m² Lift/airfoil = 3096 Nt 5160 Nt0.5*D*Af*Cl*Vt² Drag/airfoil = 193.5 Nt 322.5 Nt 0.5*D*Af*Cd*Vt² Numberof airfoils/rotor hub 12 28 Number of rotor hubs 2 2 Total lift 74,304Nt 288,960 Nt Total lift 7,582.0 kg 29,485.7 kg Total lift 16,680.5 lbs64,868.6 lbs Total lift 8.3 Tons 32.4 Tons Total airfoil drag 2,322.0 Nt9,030.0 Nt Total airfoil drive 232,200.0 Watts 903,000.0 Watts powerrequired Total airfoil drive 311.3 Hp 1210.5 Hp power required

As illustrated by Table 1, the large diameter hub of the presentinvention allows the use of a larger number of rotor blades or airfoils20 in a more efficient manner than conventional rotorcraft. This is alsoseen in FIGS. 13 and 14, which compare total lift of a conventionalhelicopter 67 to the total lift of an aircraft of the present invention10. The areas 68 under the curves in FIGS. 13 and 14 represent the totallift of each rotorcraft or aircraft as a function of rotor blade 70 orairfoil 20 length. As illustrated by FIG. 13, because lift isproportional to the blade velocity squared, conventional helicopterrotor blades or airfoils 70 provide meaningful lift over only arelatively short segment at the ends of the rotor blades 70. FIG. 14shows that comparable or superior results may be obtained using moreairfoils 20 having shorter lengths rotating about a larger diameter.

Referring again to FIG. 6, the aircraft preferably has two sets ofcounter-rotating airfoils 20. A fairing 30 is preferably non-rotatablysecured to the fuselage 12 by a support structure 72 disposed betweenthe upper and lower sets of airfoils 20. A magnetic bearing 74 isprovided on an inner portion of the fairing 30 to provide an outer track18 to further guide the airfoils 20. The outer track 18 may be formed inany number of ways, quite similar to the inner track 16 described above.For example, a stator may be secured to the fairing 30, and the statormay mate with an internal or external rotor hub. Because the forces andlift requirements at the outer track 18 will typically be less extremethan at the inner track 16, and because there should be no need fordrive means in the outer track 18, the construction of the outer track18 may be greatly simplified. For example, the stator may simply havepermanent magnets 44 disposed along upper and lower surfaces of achannel 60, and the ring hub rotor may be a simple metal hub, or a metalhub with embedded carbon fiber bands 42. Similar to the inner track 16,Halbach arrays of permanent magnets 44 may be used at the outer track 18as well.

The fairing 30 may be aerodynamically shaped to act as an airfoil duringforward movement and may be shaped to improve the stealth configurationof the aircraft. Shutters 76 may be provided to further improve theaerodynamic and stealth capabilities of the aircraft. Directional flaps78 (FIG. 5) may also be used for improved low speed directionalmaneuvering and hovering. As illustrated by FIGS. 1 and 2, rather thanemploying a simple, circular, airfoil shaped fairing 30, the fairing 30may take the shape of a more traditional fixed wing structure that maybe non-rotatably secured to the fuselage 12 by the support structure 72.This would enable an aircraft of the present invention to provide hybridcharacteristics similar to the Harrier, the Joint Strike Fighter, or theOsprey. As seen in FIGS. 1 and 2, the turbine engines 22 may be affixedto the fuselage 12, inside the circumference of the inner tracks 16, ormay be affixed to the wings 14, outside the circumference of the outertracks 18. As best seen in FIGS. 1 and 5, when the turbine engines 22are affixed to the fuselage 12, the separation of the upper and lowersets of airfoils 20 allows the use of airflow inlets 32 and jet thrustapertures 34 that pass between the upper and lower sets of airfoils 20and upper and lower inner and outer tracks 16 and 18.

The requirements for an alternator 80 needed to drive theelectromagnetic hubs of the present invention are challenging butobtainable. The alternator 80 must be compatible with jet enginerotational speeds and temperatures, controllable, lightweight, andcapable of generating large amounts of electrical power. As seen in FIG.15, a permanent magnet alternator 80 such as one developed at LawrenceLivermore National Laboratories, may be used to convert engine torque toelectrical energy for powering the electromagnetic drive of the presentinvention and may be used for flywheel energy storage. This alternator80 is capable of providing a specific power density of approximately 30kW/kG. Because of its small diameter and simple, rugged construction,this alternator 80 is able to rotate at speeds of around 30,000 rpmwithout being torn apart by centrifugal forces. The alternator 80 issimilar to a standard induction motor that is “turned inside out.” Inthat regard, the stator 82 is on the inside, and the rotor 84 is on theoutside. The stator 82 is coupled via shaft 86 to the turbine drive of ajet turbine engine 22 to provide the engine torque. A Halbach array ofpermanent magnets 88 is secured about the circumference of an innerportion of the rotor 84. Magnetic bearings 90 and a generator outputwinding 92 are secured to the stator 82. Electrical output passesthrough conductor 94. Although the alternator 80 may be a single-phasealternator, the alternator is preferably a multi-phase alternator and ismore preferably a three-phase alternator.

As seen in FIG. 16, the alternator 80 receives engine torque from and islocated near the inlet of a jet turbine engine 22. The airflow at theinlet to the engine 22 cools the alternator 80, particularly thepermanent magnets and alternator windings. The engine 22 is preferably avariable bypass engine that is capable of delivering varying amounts ofpower to the alternator 80 depending upon the needs of the system. Flapsor diverters 96 are operable to provide a variable inlet geometry.Referring to FIG. 17, the top and bottom electric motors are dividedinto multiple sections corresponding to one or more groupings of drivecoils 40. As described in more detail below, for purposes of redundancy,the drive coils 40 in the unshaded sections of upper and lower electricmotors are driven by alternator “A”, and the drive coils 40 in theshaded sections of the upper and lower electric motors are driven byalternator “B”. As also illustrated in FIG. 18, any number of engines 22and alternators 80 may be used to drive the drive coils 40 in upper andlower electric motors. For reasons to be described, as seen in FIG. 19,magnetic field bridge paths 98 can be provided to magnetically couplecorresponding sections of the upper and lower electric motors.

FIG. 20 depicts one embodiment of a system for energizing a drive coil40 of the present invention. Alternator 80 provides high frequencycurrent to alternator buss 100. Alternator buss 100 is electricallycoupled with capacitor 102, and controlled rectifiers or CRs, CR-A 104and CR-B 106, act as electronically controlled gates between thealternator buss 100 and capacitor 102. Capacitor 102 supplies lowerfrequency current to drive coil, with controlled rectifiers CR-C 108 andCR-D 110 acting as electronically controlled gates between the capacitor102 and drive coil. As seen in FIGS. 21 and 22, drive coils 40 may beinterspersed between support coils 38. As also seen in FIG. 22, eachdrive coil 40 has an associated sensor 112 that determines the polarityand position of the rotor 36 and that therefore determines when toinitiate current flow to the drive coil 40. The distribution of drivecoils 40 in between support coils 38 seen in FIG. 22 is similar to thedistribution of drive coils in the Lawrence Livermore NationalLaboratory Inductrak™ system. Although not clear from FIG. 22, the drivecoils 40 above the rotor 36 and below the rotor 36 are connected anddriven in series to make the motor thrust symmetrical. In the preferredembodiment, such as seen in FIG. 7, planes of the support and drivecoils 38 and 40 are perpendicular to minimize cross coupling.

In an alternate embodiment, the support and drive system of the presentinvention may also be used to overcome problems experienced withconventional tail rotors or lift fans 114. A helicopter typically has amain rotor that rotates about a first axis and a tail rotor 116 thatrotates about a different axis that is substantially perpendicular tothe first axis. Similarly, in an aircraft that uses a combination of ajet turbine engine 22 and a lift fan, the turbine typically rotatesabout a first axis and the lift fan rotor 116 typically rotates about adifferent axis that is substantially perpendicular to the first axis. Asseen in FIG. 23, conventional tail rotors and lift fans 114 have driveshafts 118 and transmissions or gears 120 that mechanically couple therotor 116 to an engine 22. These drive shafts 118 and gears 120 arehighly stressed, add undesirably to the weight of the craft, and sufferfrom reliability problems. The present invention eliminates the need fora drive shaft 118 and transmission 120 by using a distributed electricmotor to suspend and drive the rotor 116. As seen in FIG. 24, a seriesof permanent magnets 44 may be provided in the tip ends of the rotor116. A stator 16 may encircle the rotor 116, and the stator 16 may beprovided with support and drive coils 38 and 40 that encircle thecircumference of the rotor 116. The high efficiency electric motor driveand magnetic suspension is distributed around the circumference of thefan or rotor 116. Note that several fans can be driven in series in thismanner if additional thrust is needed. In this manner, the rotor 116need not be mechanically coupled to a drive shaft 118 or gear 120. It issimpler and more reliable to provide power to the tail rotor or lift fanrotor 116 in the form of electrical energy produced by a very compactalternator rather in the form of torque. Using a tail rotor or lift fanof the present invention reduces stress on the mechanical components,allows for the elimination of some problematic components, allows forhigher redundancy, allows for the elimination of some single pointfailure modes, and improves performance of the tail rotor or lift fan.

In operation of an aircraft such as one depicted in FIGS. 1-4, anoperator would activate the turbine engines 22 to provide power to thealternators 80. Each alternator 80 converts engine torque to electricalenergy and provides current to their portions of the upper and lowerdistributed electric motors. Because the electric motors are dividedinto sections, a single engine 22 and alternator 80 may power drivecoils 40 in both the upper and lower electric motors in the event one ormore engines 22 or alternators 80 fails. It is also important to pointout that this system provides for redundancy without the need forover-designed and heavy transmissions and cross shafts that aretypically necessary in conventional multi-engine transports andtilt-rotor systems to provide redundancy.

When the electric motors are initiated, the rotors 36 and associatedairfoil sections are at rest, resting on integral wheels or rollers. Thedrive coils 40 are activated to produce moving magnetic fields thatengage and push or pull the permanent magnets 44 in the rotor 36 toinduce rotation of the rotor 36. Rotation of the rotor 36 is increasedin a synchronous manner. Magnetic levitation of the rotor 36 is providedby the movement of the permanent magnets 44 embedded in the rotor 36past the shorted, suspension or support coils 38. Referring to FIG. 22,the movement of the permanent magnets 44 in the rotor 36 inducescurrents in the support coils 38 that produce a magnetic field thatrepels the rotor 36 magnetic field. This arrangement provides animportant safety feature. Since the magnetic levitation or support coils38 are not powered, even a complete power failure will not immediatelystop the magnetic levitation. Instead, the magnetic levitation will bepresent as long as the rotors 36, and therefore airfoils 20, are moving.This enables an operator to use auto-rotation techniques in the event ofa failure of all power systems. As discussed above in connection withFIG. 19, magnetic field bridges can be used to operably connect theupper and lower stators 16 to create low reluctance or shunt flux pathsbetween them. In normal operation, the moving magnetic fields move in acontinuous fashion about the circumference of either the top electricmotor or the bottom electric motor. In the event of a partial failure,the moving magnetic fields 122 that were continuous about thecircumference of a motor can remain continuous by traversing a lowreluctance path from the top motor to the bottom motor and by traversinganother low reluctance path from the bottom motor to the top motor.

As mentioned above, the support coils 38 may also be disposed in a “nullflux” configuration (not shown) by connecting corresponding pairs ofsupport coils 38 above and below a rotor 36 in series. In this null fluxconfiguration, the net voltage induced in the coils due to the permanentmagnets 44 in the rotor 36 moving past the coils is zero when the rotor36 is vertically centered in between the support coils 38. This approachis commonly used in the magnetic levitation of trains and has theadvantage of minimizing the circulating currents and thus reducing thepower dissipated in the coils when the rotor 36 is centered. When therotor 36 deviates from the central symmetrical position, the inducedcurrents rapidly increase to produce the levitating magnetic field.

A variable frequency current is provided to the drive coils 40 toprovide for different rotational speeds by the rotor 36. In theconfigurations depicted FIGS. 20-22 for producing the variable frequencycurrent through the drive coils 40, the high frequency alternator buss100 is used to charge the central capacitor 102. Referring to FIG. 20,the CRs are electronically controlled gates that permit current to flowonly in the direction of the arrows. CR-B 106 is closed until thecapacitor 102 is charged to a positive voltage. After CR-B 106 isdeactivated at an alternator 80 current zero and the associated sensor112 (FIG. 22) determines the magnetic field of the rotor 36 is in thecorrect position, CR-D 110 is closed to produce a positive half cyclesinusoid in the drive coil and reverse the voltage on the centralcapacitor 102. The half cycle current produces a magnetic field thatrepels the rotor 36 magnetic field to move the rotor forward. During theinitial half cycle current, the control voltage is removed from CR-D 110which then ceases conduction when the current returns to zero. When thesensor 112 determines that the rotor 36 has moved to present theopposite polarity of magnetic field, CR-C 108 is closed to generate thenegative half cycle and return the capacitor 102 voltage to a positivepolarity. As the rotor 36 speed increases, the delay between thepositive and negative half cycles of current in the drive coil isreduced such that the delay is zero at maximum rotor 36 speed. Note thatCR-A 104 and CR-B 106 can be controlled to add electrical energy to thecentral capacitor 102 when the capacitor 102 voltage is negative orpositive to replace the energy lost in moving the rotor 36.

The drive coils 40 may be connected in series or parallel combinationsor may even be operated individually to provide the maximum redundancyand to match the impedance of the alternators. If drive coils 40 areprovided above and below the rotor 36, the drive coils 40 are driven inseries to make the motor thrust symmetrical. Any number ofconfigurations may be employed to provide the driving force to rotatethe rotor 36 relative to the stator 16, including configurations that donot use capacitors, in which case, the system is designed to deliveronly the energy required to drive the rotor 36 and to replace the energydissipated in the coil resistance while storing minimum energy. Thepower delivery system of the present invention is extremely redundantand reliable due to the distributed drive locations, the common powerbuss, and multiple power sources. Note also that the azimuthalorientation of the craft is dependent upon the net torque differentialin the top and bottom electric motors. Accordingly, preciselycontrolling the number of drive sections that are actuated can be usedto orient the craft precisely to any direction of travel. Using theinternal rotor hub 36 configuration as depicted in FIG. 7 simplifies theconstruction and operation of the electric motors. For example, iteliminates the need to use a Halbach array of permanent magnets. It alsopermits the rotor hub 36 to expand radially as its speed increaseswithout loss of magnetic interaction and repulsion.

One advantage of an aircraft of the present invention 10 over aconventional helicopter is the possibility of higher lift capability fora given diameter system. One important aspect of the present inventionis that it can be operated in hover mode by reducing the blade attackangle, thereby generated the same downwash as a conventional helicopter.Another important aspect of the present invention is that, by increasingthe pitch angle, an aircraft of the present invention 10 will offerhigher climb rates, higher load capabilities, and more versatility. Anaircraft of the present invention also differs from a conventionalhelicopter in that it offers more options for forward propulsion. Ofcourse, the airfoils 20 used for VTOL operations may also be used forhorizontal flight by tilting the rotor 36 plane to provide a portion ofthe downward thrust vector in the forward or rearward direction, verysimilar to horizontal propulsion of a conventional helicopter. Low speedhorizontal maneuvering may also be accomplished using directional flapsor slats 78 that direct the downward airflow rearward, forward, or tothe side (FIG. 5). This method of maneuvering is capable because of thepresence of a body or fuselage 12 at the inner circumference of therotor hub 36 and the presence of a fairing 30 encircling the outercircumference of the airfoils 20. Accordingly, this mode of operation isnot possible in conventional helicopters or in tilt-rotor systems. Highspeed transport is also possible, such as by using a variable bypass jetturbine engine 22 (FIG. 16) that also powers the alternator 80. DuringVTOL operations, flaps 96 are closed to provide the maximum power to thealternator 80 and to minimize the thrust fan load. During the transitionto horizontal flight, flaps 96 are opened to transfer power to thethrust fans 124. As the load on the alternator 80 is decreased, the flowthrough the fan is increased to transfer the power flow to the fan toobtain maximum forward thrust The directional flaps or slats 78 (FIG. 5)may also be used to divert the downwash 126 from the airfoils 20 foradditional thrust. As the horizontal speed increases, the fairing 30 andwings 14 provide increasing portions of the lift reducing the load onthe airfoils 20, until the thrust of the turbine engines 22 is used topower horizontal flight as in a conventional jet aircraft. At thispoint, the airfoils 20 are operated at or near zero pitch.

Violent downwash 126 is a concern during VTOL and VSTOL operations,particularly for heavy lift tilt-rotor systems 128, and the presentsystem offers advantages in addressing downwash 126 concerns. Referringto FIGS. 25 and 26, during VTOL operations, the total downwash 126 fortwo systems with the same load and same diameter are identical. FIGS. 25and 26 illustrate the very chaotic interaction of the downwash 126patterns of a multi-tilt rotor system 128 and the uniform downwash 126pattern of an aircraft of the present invention 10. The total magnitudeof the downwash 126 for both systems must be the same in order to liftthe same loads, but the aircraft of the present invention 10 creates adownwash 126 that is distributed around the circumference of the systemdiameter, whereas the tilt-rotor 128 downwash 126 is much more locallyintense and interactive. In addition, the downwash 126 from an aircraftof the present invention can be dispersed using vanes on the undersideof the aircraft to make the impact of the downwash 126 on the groundless than that of the downwash from the tilt-rotor system.

An aircraft of the present invention 10 offers many advantages overconventional rotorcraft and fixed wing aircraft. The use of counterrotating sets of airfoils 20 eliminates the need for a tail rotor andprovides a very stable platform. The large diameters and circumferencesof the rotor hub 36 and stator 16 allow the use of a large number ofairfoils 20 for additional lift. The large diameters and circumferencesof the rotor hub 36 and stator 16 also make it easy to use additionalengines 22 and alternators 80, without heavy, complex, unreliablemechanical linkages, to power the electric motors for heavy dutyapplications or for redundancy. The large diameters and circumferencesof the rotor hub 36 and stator 16 also spread the aircraft and loadweight over a much larger area such that the magnetic bearingrequirements are reasonable and the total lift capacity is much largerthan that of other approaches. For example, an aircraft using a Halbacharray configuration of permanent magnets 44, such as used in FIGS. 6 and8, can generate a magnetic repulsive force that can support 40 metrictons per square meter of surface area (4 kG/cm² or 56 lb/in²) at avelocity of approximately 20 m/s. This is approximately 8 times themaximum lift generated by an airfoil of 7 lbs/in². As illustrated inTable I, above, an aircraft of the present invention 10 with a rotor hub36 diameter of approximately 10 m would be capable of providing lift ofgreater than approximately 30 tons.

In addition to the readily apparent civilian uses for the presentinvention, the heavy lift capabilities and air mobility of aircraft ofthe present invention 10 might provide several advantageous militaryapplications. For example, the heavy lift capabilities and large amountsof electrical power onboard make an aircraft of the present invention anideal platform for many heavy electric weapons, such as electromagneticguns, lasers, and particle beams. The aircraft provides air mobility,fast response and deployment, and the engines 22 and alternators 80 usedfor VTOL operations may also be employed to provide a large amount ofelectrical power to weapons systems. Further, the use of the rotatingrotor hubs 36 as flywheel energy storage enables electric weaponsapplications to be used in flight. The use of a fairing 30 and shutters76 to enshroud the airfoils 20 increases the efficiency of the airfoils,reduces audible noise, and enables stealth technologies to be betterdeployed in a rotorcraft. Further still, the aircraft is relativelyquiet, stealthy, and fast and is capable of carrying large loadsincluding armor, personnel, and weapons. The aircraft also providestransportation that is not hampered by common obstacles such as terrain,land mines, water, and rivers, and its VTOL capabilities mean that norunways or landing strips are required.

Other modifications, changes and substitutions are intended in theforegoing, and in some instances, some features of the invention will beemployed without a corresponding use of other features. For example, theaircraft may be used with or without a fairing 30. Also, The supportcoils 38 and drive coils 40 may be disposed and powered in any number ofways. Further, the stator 16 and rotor hub 36 may take any number ofshapes and sizes and may be operably coupled in any number of ways.Further still, any number of ways may be used to supply power to theelectric motors, and drive coils 40 may be used to push or pull theappropriately aligned magnets 44. It is of course understood that allquantitative information is given by way of example and is not intendedto limit the scope of the present invention. Accordingly, it isappropriate that the appended claims be construed broadly and in amanner consistent with the scope of the invention.

1. An aircraft, comprising: a fuselage; a first stator secured to saidfuselage, wherein said first stator comprises a magnetic bearingcomprising a plurality of permanent magnets arranged in a Halbach array;a first set of drive coils secured to said first stator; a first rotorhub operably coupled to said first stator; a first plurality of airfoilssecured to said first rotor hub; and wherein said first rotor hubcomprises: a first metal ring; and a plurality of carbon fiber bandsdisposed within said first metal ring.
 2. The aircraft of claim 1,further comprising: a second stator secured to said fuselage, whereinsaid second stator comprises a magnetic bearing comprising a pluralityof permanent magnets arranged in a Halbach array; a second set of drivecoils secured to said second stator; a second rotor hub operably coupledto said second stator; a second plurality of airfoils secured to saidsecond rotor hub; and wherein said second rotor hub comprises: a secondmetal ring; and a plurality of carbon fiber bands disposed within saidsecond metal ring.
 3. The aircraft of claim 2, wherein said firstplurality of airfoils rotates in a first direction, and said secondplurality of airfoils rotates in a second direction.
 4. The aircraft ofclaim 3, wherein said first direction is one of clockwise andcounterclockwise, and said second direction is opposite said firstdirection.
 5. The aircraft of claim 2, further comprising at least twoengines secured to said fuselage.
 6. The aircraft of claim 5, furthercomprising a number of alternators equal to the number of said engines,wherein each of said alternators is operably coupled to one of saidengines whereby said alternators are powered by said engines.
 7. Theaircraft of claim 6, wherein at least one of said alternators isoperably coupled to a first subset of said first set of drive coils anda first subset of said second set of drive coils, at least one other ofsaid alternators is operably coupled to a second subset of said firstset of drive coils and a second subset of said second set of drivecoils, and each of said first and second sets of drive coils are evenlydistributed around a circumference of the aircraft.
 8. The aircraft ofclaim 1, further comprising a plurality of wings non-rotatably attachedto said fuselage.
 9. An aircraft, comprising a fuselage; a first statorsecured to said fuselage, wherein said first stator comprises a firstmagnetic bearing comprising a plurality of permanent magnets arranged ina Halbach array; a first set of drive coils secured to said firststator; a first rotor hub operably coupled to said first stator; a firstplurality of airfoils, wherein each of said first plurality of airfoilscomprises a proximal end and a distal end, and each of said firstplurality of airfoils is connected to said first rotor hub at saidproximal end; a fairing non-rotatably secured to said fuselage; a firstmagnetic bearing secured to said fairing, wherein said distal ends ofsaid first plurality of airfoils are operably coupled to said firstmagnetic bearing; a first auxiliary bearing at a circumference of theaircraft in proximity to the first hub, said auxiliary bearingcomprising a plurality of permanent magnets; and a first plurality ofpitch control arms, each of said first plurality of pitch control armsconnected to one of said first-plurality of airfoils and operablyengaged with said first auxiliary bearing, whereby a pitch of each ofsaid first plurality of airfoils is adjusted by manipulation of saidfirst plurality of pitch control arms.
 10. The aircraft of claim 9,further comprising a second stator secured to said fuselage, whereinsaid second stator comprises a second magnetic bearing comprising aplurality of permanent magnets arranged in a Halbach array; a second setof drive coils secured to said second stator; a second rotor huboperably coupled to said second stator; a second plurality of airfoils,wherein each of said second plurality of airfoils comprises a proximalend and a distal end, and each of said second plurality of airfoils isconnected to said second rotor hub at said proximal end; a secondmagnetic bearing secured to said fairing, wherein said distal ends ofsaid second plurality of airfoils are operably coupled to said secondmagnetic bearing; a second auxiliary bearing at a circumference of theaircraft in proximity to the second hub, said second auxiliary bearingcomprising a plurality of permanent magnets; and a second plurality ofpitch control arms, each of said second plurality of pitch control armsconnected to one of said second plurality of airfoils and operablyengaged with said second auxiliary bearing, whereby a pitch of each ofsaid second plurality of airfoils is adjusted by manipulation of saidsecond plurality of pitch control arms.